Objective: The present study aimed to predict Tanzanian medical students' Voluntary Counseling and Testing (VCT) participation intention using the Health Belief Model (HBM) as a theoretical framework. Further, differences between respondents who had previously participated in VCT and respondents who had not were assessed. Methods: Cross-sectional data were gathered from 186 Tanzanian medical students using a self-administered questionnaire. Results: Almost half of the respondents (43.3%) reported having been tested for HIV. A prediction model containing HBM and demographic variables explained 31% of the variance in VCT-participation intention. Self-efficacy, fear of being HIV-positive, and perceived susceptibility contributed significantly to the final regression model. In addition, respondents who had previously participated in VCT expressed less fear of being stigmatized and being HIV-positive than respondents who had not. Conclusion: Fear of being HIV-positive, self-efficacy, perceived susceptibility and fear of being stigmatized were associated with either VCT-participation intention or previous participation. Further, the HBM accounted for a limited proportion of the explained variance in Tanzanian students' intention to participate in VCT. This suggests that the validity of the HBM in explaining HIV-preventive behavior in Sub-Saharan Africa should be questioned. Practice implications: Interventions promoting VCT should incorporate program elements targeting self-efficacy, fear of being HIV-positive, perceived susceptibility and fear of being stigmatized. © 2008 Elsevier Ireland Ltd. All rights reserved.